During the operation of a magnetic resonance facility, a perceptible noise pattern is known to occur as a result of the operating technology. Consequently, an examination patient who is examined using a magnetic resonance facility must wear a hearing protection, wherein this must ensure that the loudness level does not exceed 99 bBa at the ears of the patient.
A known hearing protection which is often also called capsule hearing protection consists of two ear covers which normally fit closely onto the ear, or onto the head around the ear, over padding. The covers are connected together via a clip, which can be telescoped such that the hearing protection can be adapted to the head size, and are usually pivotably attached to the clip. Known covers consist of an almost semi-spherical or domed plastic shell which is curved outwards and inside which a thin foam inlay is arranged, wherein the annular ear padding is arranged in the area facing the head. The curvature of the mainly oval outer shell is usually not symmetrical, said outer shell instead curving further outwards in the lower section, which is further from the clip, than in the upper section. The shell itself encompasses a relatively large volume which is sealed relative to the head via the ear pad. The attenuation is primarily due to the fact that a relatively large volume is encapsulated via the outer shell. The internal foam part contributes little to the actual noise attenuation and serves primarily to attenuate the perception of the noise of the blood.
Such a hearing protection having a construction of considerable width can be used for a range of examinations in magnetic resonance facilities because there are no space problems. In the case of examinations in the head and neck area, however, special surface coils called head coils or head-neck coils must be positioned next to the patient in order to allow the recording of meaningful magnetic resonance images. The coils, which are normally designed in the form of a cage, must be arranged as close as possible to the head of the patient in this case. A hearing protection of the type cited at the beginning cannot be used in such cases since said hearing protection often cannot be properly applied or the coils cannot be properly positioned. Consequently, use is often made of simple foam covers which can be placed over the ears of the patient and pushed underneath the head coil or head-neck coil. The sound protection that can be achieved hereby is relatively modest and the noise stress of the patient is therefore high.
The German utility model DE 82 06 723 U1 discloses a hearing protection shell, wherein an attenuating inlay is fastened in the shell by means of a retainer ring, wherein the retainer ring and the shell part are connected together by means of a snap-on arrangement. A sound-absorbing material is provided as an attenuating inlay.
DE 33 12 801 A1 discloses a hearing protection device which additionally includes built-in electromechanical components for generating signals which are similar to a heart rhythm. A sound-absorbing elastic material, in particular foam rubber, is proposed as a noise protection inlay in this case. Nothing is disclosed in relation to the fastening of the noise protection inlay.
The British patent specification GB 860,030 discloses a hearing protection device whose hearing protection earpiece can be adjusted in its orientation. It is also mentioned here that the earpieces can preferably be filled with a noise-attenuating material such as plastic foam or foam rubber.
The international patent application WO 02/060365 A1 discloses a method for producing a hearing protection earpiece. In this case, it is again proposed that provision be made for a foamed noise-attenuating plastic material within the earpiece.
DE 695 13 502 T2 is concerned with a disc connection for a hearing protector, wherein a sealing disc can be attached to the hearing protection earpiece in a simple and re-releasable manner and taken off again. The sealing cushion element of a capsule hearing protection is therefore exchangeable. The manner in which the noise attenuation occurs is not described.
A head fixing apparatus for an imaging medical examination device is described in DE 102 45 487 A1. In this case, the fixing cushions are shaped so as to form a chamber that encloses an ear when they are fixed. Sound is pneumatically transferred into this chamber via an air duct.
The invention therefore addresses the problem of specifying a hearing protection which, even in the case of examinations involving head coils and head-neck coils, can readily be used and integrated in the coil, and which offers an adequate sound protection at the same time.
In order to solve this problem in the case of a hearing protection of the type cited at the beginning, provision is made for a compact inner part to be arranged in and permanently connected to the plastic outer shell, said inner part consisting of a dimensionally stable plastic mass and essentially filling the outer shell completely.